Halide Ion Hydration: Big Challenges from Small Ions
Gregory S. Tschumper*
Department of Chemistry and Biochemistry, University of Mississippi University, MS 38677-1848
*Presenting author: tschumpr@olemiss.edu
The challenges of reliably modeling the OH stretching vibrations in small water clusters can exacerbated when small halide ions are introduced to the system. This work reports MP2, CCSD, CCSD(T), CCSDT, CCSDT(Q) and CCSDTQ structures, energetics and harmonic vibrational frequencies of monohydrated halide complexes (X– /H2O where X = H, F, Cl, Br and I). Despite providing very similar electronic dissociation energies, exceptionally large deviations between the MP2 and CCSD(T) harmonic vibrational frequencies are observed with a wide variety of basis sets for F– and H– (often exceeding 100 cm–1 for the former and 300 cm–1 for the latter). CCSDT, CCSDT(Q) and CCSDTQ computations are being performed to examine higher-order correlation effects on these energetic and spectroscopic properties of the X– /H2O systems.